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Date: Thu, 5 Oct 2017 06:42:38 +0900 From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp> To: hannes@...xchg.org Cc: akpm@...ux-foundation.org, alan@...yncelyn.cymru, hch@....de, mhocko@...e.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org, kernel-team@...com Subject: Re: [PATCH 1/2] Revert "vmalloc: back off when the current task is killed" Johannes Weiner wrote: > On Thu, Oct 05, 2017 at 05:49:43AM +0900, Tetsuo Handa wrote: > > On 2017/10/05 3:59, Johannes Weiner wrote: > > > But the justification to make that vmalloc() call fail like this isn't > > > convincing, either. The patch mentions an OOM victim exhausting the > > > memory reserves and thus deadlocking the machine. But the OOM killer > > > is only one, improbable source of fatal signals. It doesn't make sense > > > to fail allocations preemptively with plenty of memory in most cases. > > > > By the time the current thread reaches do_exit(), fatal_signal_pending(current) > > should become false. As far as I can guess, the source of fatal signal will be > > tty_signal_session_leader(tty, exit_session) which is called just before > > tty_ldisc_hangup(tty, cons_filp != NULL) rather than the OOM killer. I don't > > know whether it is possible to make fatal_signal_pending(current) true inside > > do_exit() though... > > It's definitely not the OOM killer, the memory situation looks fine > when this happens. I didn't look closer where the signal comes from. > Then, we could check tsk_is_oom_victim() instead of fatal_signal_pending(). > That said, we trigger this issue fairly easily. We tested the revert > over night on a couple thousand machines, and it fixed the issue > (whereas the control group still saw the crashes). >
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